Help Trying To Fix Extended Magazine

I recently acquired an M17 off a friend of mine that came with two magazines and a broken extended mag, and now I'm looking to fix up the latter.Now the Magazine still has all the gas component parts and still holds gas rather well, the problem is that one day the base plate fell off, along with the spring, follower, and the piece that is like part #234 on the normal magazines, and the pin that holds that piece.
I went on the pro shop and could only find the magazine follwer,which is out of stock, and am wondering how can I get my hands on all the pieces so I can get this thing working.